1. Field of the Invention
The invention relates to optical storage devices, and in particular, to blank detection for an optical disc.
2. Description of the Related Art
FIG. 1a shows a conventional optical storage device. Conventionally, data stored in an optical disc is amplified and digitized to a target level before decoding. The various gain amplifier 102, analog to digital converter 104 and auto gain controller 106 form an AGC loop to adjust the gain of the RF signal #RF. An extra data path is formed by a blank detection unit 110 to detect blankness of the RF signal #RF. If amplitude of the RF signal #RF is below a predetermined threshold, the decoder 108 is not enabled to decode data, and the corresponding sector is reported as blank. Otherwise, if the RF signal #RF is not blank, the blank detection unit 110 sends an enable signal #en to the decoder 108, enabling the decoder 108 to decode the data signal #DATA output from analog to digital converter 104.
FIG. 1b is a schematic view showing the definition of blankness. When the amplitude of the RF signal #RF is below the threshold (+th and −th), the corresponding sector where the RF signal #RF is obtained is reported as a blank sector. When the amplitude of RF signal #RF exceeds the threshold, the decoder is enabled to decode the data signal #DATA.